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Hybrid Electric
Vehicle
A Dolcera Report
December 2005
Rationale
Automobiles are a source of considerable pollution at the global level, including
a significant fraction of the total greenhouse gas emissions.
•
On July 22, 2002 California Governor Gray Davis signed into law AB 1493
(commonly known as the "Pavley law") — precedent-setting legislation to reduce
global warming pollution from motor vehicles.
•
This bill directs the California Air Resources Board (CARB) to develop and adopt
regulations that achieve the maximum feasible and cost-effective reduction of
greenhouse gas emissions (GHG) from passenger cars and light trucks sold in
California.
Source: http://www.ucsusa.org/clean_vehicles/vehicles_health/californias-global-warming-vehicle-law.html)
Development I
The new millennium is bringing a millennial change to the
family car. A few years back, the key concerns were:
• Pollution,
• Nagging worries about global warming, and
• Oil shortages.
These concerns led to the development of Electric Vehicle
(EV’s) powered by batteries. But current battery
technology does not provide EV's with a range that is
acceptable to consumers.
Limitations of EV’s:
• An average commute to work is around 40 miles.
• EV's have a range of 80-100 miles using advanced battery
technology.
• While batteries need frequent recharging, they are not the only
way to power an electric car.
Development II
HEV is just the first step in reducing the environmental
impacts of automobile use with out loosing-off comforts,
performance, storage room and extended driving range.
Advantages of HEV’s
• HEV contains parts of both gasoline and electric vehicles in
an attempt to get the best of both worlds.
• HEV is able to operate nearly twice as efficiently as
traditional internal combustion vehicles.
• Equivalent power, range, cost and safety of a conventional
vehicle while reducing fuel costs and harmful emissions.
• The battery is continuously recharged by a motor/generator
driven by the ICE or by regenerative braking.
Components of HEV Battery system
The batteries in a HEV are the energy storage device for the electric
motor. Unlike the gasoline in the fuel tank, which can only power the
gasoline engine, the electric motor on a hybrid car can put energy into the
batteries as well as draw energy from them.
• Battery:- Two or more electrochemical energy cells connected together to
provide electrical energy.
• Generator:- The generator is similar to an electric motor, but it acts only to
produce electrical power.
• Electric motor:- Advanced electronics allow it to act as a motor as well as
a generator. For example, when it needs to, it can draw energy from the
batteries to accelerate the car. But acting as a generator, it can slow the
car down and return energy to the batteries.
• SOC:- The State of Charge of a battery is its available capacity expressed
as a percentage of its rated capacity.
HEV layout
Wheel
Generator
Transmission
Wheel
Wheel
IC Engine
Battery
Motor
Scenario 2: Braking – Kinetic energy is
converted to electric energy during
regenerative braking by electric motor
and supplied to battery.
Wheel
Motor
Scenario 3: High speed – Power is
provided by IC engine and electric motor
via generator. Generator also charge
battery during high speed.
IC Engine
Generator
Transmission
Wheel
Generator
Transmission
Wheel
Scenario 1: Low speed - Power is
provided by electric motor using energy
supplied by the DC battery
IC Engine
Motor
Battery
Battery
HEV battery system design parameters
Factors affecting battery performance
•
Temperature:- Battery performance is highly dependent on temperature.
each type of battery works best within a limited range of temperatures.
Battery age/Shelf life:- Corrosion is the main component behind decreased
performance in lead acid type batteries by age.
Depth of discharge:- Batteries are able to maintain their performance longer
when they are not deeply discharged regularly.
•
•
Design parameters:
•
•
•
•
•
•
•
How much space is available for the batteries?
How much can they weigh?
What is the desired range?
What is the weight of the vehicle?
What is the targeted vehicle cost?
How will the batteries be recharged and
What kind of drive system requirements is needed?
These are necessary questions because of the variety of battery types
available and the differences between them. The chart below lists the
characteristics of the most common types of batteries.
Source: http://www.atti-info.org/technology/ev_tech.html
Types of HEV’s batteries and performance
There are many types of batteries that are currently being used - or being developed for
use - in HEVs. The following table lists these types along with their common
characteristics. The types are listed in descending order of popularity for use in HEVs,
with the most popular choices at the top of the table. Source: http://www.atti-info.org/technology/ev_tech.html
Self
Energy Power
Discharge Current Future
Cycle
Battery Type Density Density
Rate
Cost
Cost Vehicles Used_In Other Notes
Life
[Wh/kg] [W/kg]
[% per [$/kWh] {$/kWh]
month]
CARTA bus,
25 to 75 to 200 to
100 to
Lead-Acid
2 to 3
75
Solectria E10
35
130
400
125
(sealed)
Potential: 55
Audi Duo, GM
Advanced 35 to 240 to 500 to
Wh/kg, 450
EV1 (VLRA),
Lead Acid
42
412
800
W/kg, and 2000
Solectria Force
cycle life
Toyota RAV4-EV,
Toyota Prius,
Potential: 120
Nickel-Metal 50 to 150 to 600 to
525 to 115 to
Chrysler Epic
Wh/kg, and
Hydride
80
250 1500
540
300
minivan, Honda 2200 cycle life
EV, Chevy S-10
Nickel35 to 50 to 1000 to
300 to
Potential: 2200
10 to 20
110 WWU Viking 23
Cadmium
57
200 2000
600
cycle life
100 to
400 to
Potential: 1000
Lithium-Ion
300
Nissan Altra EV
150
1200
Wh/kg
Zinc56 to
100
500
300
Bromide
70
Lithium
100 to 100 to 400 to
100
Polymer
155
315
600
NaNiCl
90
100
400
110 to
240 to
Zinc-Air
100
300
100
200
450
Vanadium
50
110
400
300
Redox
Comparison of top 3 batteries used in HEV’s
Lead Acid
Advanced Lead Acid
Nickel-Metal Hydride
Low cost
Longer cycle life than conventional lead acid.
High cost
Low energy density
Valve regulated lead/acid (VLRA)
batteries are showing great promise.
Higher energy density than lead acid not as
susceptible to heat
Longer recharging time (as 6 to 8 hours)
Shorter recharging time
Only fair cycle life
Can be ruined by completely discharging
them.
During recharging it is important to maintain the balance of battery. The balance of battery is maintained by
controlling battery from
•
•
Overcharging and
Over discharging
Controlling is achieved by defining State of Charge of battery
•
•
Upper limit value – overcharge and
Lower limit value – over discharge
When overcharge is detected power generation is controlled/cut-off and when over discharge is detected
power supply to electric motor is stopped. Detection is achieved by appropriate sensors.
This report investigates various procedures available/adopted by various assignees in order to maintain
balanced battery pack by avoiding overcharge and/or over discharge.
HEV battery system concerns
The ultimate goal of HEV can only be achieved with the balance battery pack.
Since the main source of energy in HEV is batteries and recharging is carried
out on-board.
Advantages of balance battery pack:
•
Balancing of battery SOC’s increases battery life
•
Automated balancing circuitry will decrease overcharging
(and gassing) and decrease manual maintenance.
This in turn provides
• Equivalent power range at low cost as conventional vehicle while
reducing fuel costs and harmful emissions.
• Can travels twice the distance of a conventional vehicle on the
same amount of energy.
Objective
The present report attempts at finding out various aspects and
approached involved in maintaining balanced battery through patent
and non-patent information. Few patents have been selected to
identify:
• IP activity over years
• Competitors
• Competitor and Market Landscape
• Technology map – Based on patent technology focus
• Technology approach - Competitor’s
IP activity over years
The activity graph displays patenting activity over years in the area of
overcharging of HEV battery. The problem seem to be quiet old, the
graph indicates first attempt was made in 1978 to solve the problem
Since then there has been continuous efforts with high and low activity
through out. The graph indicates thick IP activity during 1995-1997S.
4
3
3
3
3
2
2
2
2
1
No. of patents
1
1
1
1
0
0
0
0
1978
1992
1993
1994
1995
1996
1997
1998
Priority year
1999
2000
2001
2002
2003
Assignee wise IP activity
Companies with most HEV battery patents are arranged in decreasing
order in below graph. Top three players are Nissan motors with (5) patent
records to its credit, followed by Toyota with (4) and Acqueous (3).
6
5
5
4
4
3
3
1
1
1
1
1
1
GENERAL
MOTOR
HONDA
MOTORS
HYBRICON
SANYO
ELECTRIC
SUZUKI
MOTORS
1
FORD
MOTORS
2
1
LOCKHEAD
MARTIN
ACQUEOUS
TOYOTA
MOTORS
0
NISSAN
MOTORS
No. of patents
Assignees
Competitor and Market Landscape
The below left graph display assignee wise IP activity over years, according to the present data the
very first patent pertaining to HEV battery charging system was filed by HYBRICON in 1978 but not in
the race anymore. Though NISSAN, AQUEOUS and TOYOTA seems be ahead in acquiring max.
number of patent to their credits, but not active since 2000. GM and HONDA have bagged a singlesingle patent of same age in 2003.
The below right graph display market (countries) eyed by various competitors. The hot market place
for most competitors is Japan (17) followed by United States (11) and Germany (04). According to the
present data Nissan seems to be having strong presence in Japan market than rest with 5 patents
protected, followed by Aqueous and Toyota
We will look in to their technologies in competitor approaches section coming latter in the report.
Distribution of patents based on technology focus
The above pie chart displaying various factors that has affect on battery charge and discharge and numbers
indicating the distribution of patents in that area from selected list of patents. The distribution of patents is based
on technology focused in the patent.
• Power generation: Technologies disclosed in patents for modes of power generation in HEV for
charging battery and ways of handling
• Power management: Technologies disclosed in patents for managing the battery balance during power
generating and/or consuming
• Fluctuating HEV operating mode: Technologies disclosed in patents for managing battery balance
during fluctuating operating modes, especially in composite HEV
• Power supply: Technology disclosed in patent for starting engine with auxiliary battery current when
main battery current is not sufficient to start engine
Technology map – Based on patent technology focus
Patent number/
Priority year
Power Generation
Power management
Fluctuating hybrid
operating mode
Power Supply
Series/parallel
HEV
US6583599 (2003)
-
-
Operating the starter/
Alternator as a motor.
-
PHV
JP08098321 (2003)
-
-
SPHV forcibly run as SHV
-
PHV
US6504327 (2000)
-
-
Motor driving stop or off Upper & lower limiting voltage
-
SHV
US5550445 (2000)
-
Comparing battery voltage
With predetermined value
-
-
SHV
US6809501 (2000)
Idling in slow traffic
-
-
-
SHV
US5722502 (1995)
-
US4351405 (1999)
High speed
-
-
-
PHV
JP2001078306 (1997)
Regenerative braking
-
-
-
PHV
JP06055941 (1997)
Regenerative braking
-
-
-
SPHV
JP10295045 (1997)
Regenerative barking
-
-
-
SHV
JP06319205 (1996)
Regenerative braking
-
-
-
SHV
JP2001268707 (1996)
Restarted after an
idiling stop released
-
-
-
SHV
JP10084636 (1995)
-
Regulating number of
rotations of IC engine
-
-
PHV
JP09200907 (1995)
-
Control unit stops
generator output
-
-
PHV
JP11136808 (1994)
-
Controlling generated power
of a generator
-
-
SHV
-
PHV
JP09117010 (1993)
SHV mode or continuous-type PSHV mode is controlled by
driver or based on the SOC of the accumulator.
-
Operates generator at number of revolution
corresponding to number of revolutions of IC engine
-
-
-
Assignee
PSHV
US5828201 (1993)
-
Maintaining charge capacity
of battery modules
-
-
SHV
US20050038576 (1992)
-
Suppressing the engine
torque vibration
-
-
SPHV
US6392380 (1978)
-
-
-
Automotive elec. system
battery is used to starts engine
SHV
AQUEOUS
AQUEOUS
AQUEOUS
Clustering – Technology focus
Event
Output
Effect
Action
Various methods of
Power management
Comparing battery voltage
With predetermined value
Regulating number of
rotations of IC engine
Control unit stops
generator output
High speed
Regenerative braking
Power generated/
consumed
Restarted after an
idiling stop released
Overcharge
Power management
Controlling generated
power of a generator
Over discharge
Operates generator at
number of revolution
corresponding to number
of revolutions of IC engine
Maintaining charge
capacity of battery modules
Suppressing the engine
torque vibration
Operating the starter/
Alternator as a motor.
Fluctuating hybrid
operating mode
SPHV – Series/Parallel Hybrid Vehicle
SHV – Series Hybrid Vehicle
Power generated/
consumed
Overcharge
Power management
SPHV forcibly run as SHV
Over discharge
Motor driving stop or off Upper & lower limiting voltage
Technology approach – Competitor’s
In technology approach patent and non-patent literature is used to extract information about the technology
profile of various assignees such as
•
•
•
•
•
•
•
•
Years in this activity
Type of batteries used
Battery charging system
Type of HEV (Series (SHV)/Parallel (PHV)/Composite (SPHVS))
Technology strength based on citation analysis
Product Vs patent identification
Battery management solutions proposed (i.e. current control/cut-off system and SOC detection
technique)
Scientific literature and technology news to strengthen the report, since patent activity is a slow
process.
TOYOTA MOTORS - Technology approach
Battery type: Lead-Acid battery
Battery charging system:
The charge to a DC-battery is provided by the generating power from a generator and the regeneration power
from the drive motor at the time of braking.
Patent #/Priority date
Current control/Cut-off system
SOC detector
US5550445 (1993)
During heavy load state, generator
output is controlled to be increased
and motor output is restricted. When
heavy load is not detected, generator
and motor output is stopped or avoided
thus preventing battery overcharging.
Voltage sensor and an SOC sensor detect a
voltage and an SOC of the battery and feed the
detected results to the controller.
JP08098321 (1994)
When the charged state of a battery is
out of a first control target range, the
ECU makes the SPHV forcibly run as
the SHV. With this constitution, even if
the PHV running is continued for a long
time, the charged state of the battery is
controlled with a certain frequency, so
that the overcharge or over discharge
of the battery can be avoided.
The SOC sensor detects SOC of a cell and the
voltage sensor detects the electrical potential
difference of a cell for the rotational frequency of
a motor.
JP09200907 (1996)
The
generation-of-electrical-energy
output of a generator is suspended by
the time it reaches the electricalpotential-difference upper limit limiting
value of the DC-battery.
SOC is controlled within proper limits. If SOC falls
from a lower limit, a generator will be operated by
the maximum output, and if SOC exceeds a
upper limit, a generator will be operated with the
minimum output.
US5722502 (1995)
Overcharging is prevented by using
mechanical loss of engine, generator
and the torque distributing system.
ECU shift to SHV mode during
discharging (i.e. Heavy load) is thus
preventing battery from discharge.
SOC sensor detects accumulator SOC and SOC
is maintained to the desired range by using forced
mode control.
Series/parallel composite
electric vehicle (SPHV)
TOYOTA MOTORS - Technology approach
Event
Output
Effect
Action
Heavy load- generator o/p is
controlled to be increased and the
o/p of the motor is restricted.
No heavy load- The increase
control of the generator output and
the output limit of the motor are
stopped or avoided.
US5550445 (1993)
High speed
JP08098321 (1994)
Fluctuating hybrid
operating mode
Power generated/
consumed
JP09200907 (1996)
Regenerative braking
US5722502 (1995)
Fluctuating hybrid
operating mode
Various Methods of
Power Management
Overcharge
Over discharge
Power management
Overcharge/over discharge of the
battery is avoided by making
SPHV forcibly run as the SHV
(series hybrid vehicle) by an ECU
(electronic control unit) when the
charged state of a battery is out of
a first control target range.
Overcharging is avoided by
suspending the power output of a
generator by control means, when
electrical-potential-difference
value of the DC-battery reaches
upper limit.
Overcharging is prevented by
using mechanical loss of engine,
generator and the torque
distributing system. ECU shift to
SHV mode during discharging (i.e.
Heavy load) thus preventing
battery from discharge.
Findings
Product
Patent
TOYOTA PRIUS
US5722502
TOYOTA HIGHLANDER
US6691809
NISSAN MOTORS - Technology approach
Battery type:- Lead-acid and/or Nickel-Hydrogen battery
Battery charging system:The battery is charged from the power generated by the generator and regeneration power from a motor.
Electric motor functions as a generator to charge the battery when a hybrid vehicle is restarted after an idling
stop released.
Patent #/Priority date
JP10084636 (1996)
Battery
Series Hybrid
Electric Vehicle
JP10295045 (1997)
Parallel Hybrid
Electric Vehicle
JP11136808 (1997)
Forward citation JP10295045 (1997)
Year
#
1998
4
1999
4
2000
3
2001
7
2002
2
US6452286 (1999)
Current control/Cut-off system
Output of generator is restricted
depending on the battery condition
by the generator output controller.
The battery management provides
an actuator command for control of
electric power input upon charging
the battery pack in response to the
current value of BT (battery
temperature).
A control unit with a microcomputer
controls the charge/discharge of the
DC-battery by controlling the
generated power of the generator
based on the discriminated results
of the state of the DC-battery.
Control unit - Microprocessor
(42 V)
JP2001268707 (2000)
(42 V)
The charge of a DC-battery is
restricted to a proper amount by
restricting the IC engine output
torque, if the charging level SOC is
higher than a given value.
SOC detector
The DC-battery is equipped with
the
DC-battery
condition
detecting element which detects
the electrical potential difference,
temperature,
and remaining
capacity.
A controller finds the charging
amount SOC of the battery on
the basis of the terminal voltage
VB and the temperature TB of
the battery.
DC-battery condition distinction
means distinguish the condition
of a DC-battery and a generated
output decision means opt for
the generated output by the
engine driven generator based
on the distinction result by the
dc-battery condition distinction
means.
Charging current detecting unit
detects the actual charging
current of the motor-generator
and actual charging current to
the high voltage battery by a
current sensor.
When start conditions are met,
the charging level SOC of the
battery is detected by the current
sensor.
Scientific Literature
(Non-patent info)
In 1998, developed high power
density Li-ion battery for parallel
HEV (Jidosha)
In 1999, developed thermal design
of battery packs for HEV (Japan
Journal of Thermo physical
Properties,)
In 2000, developed electric double
layer capacitor for HEV with high
charge/discharge efficiency at high
power density (Jidosha)
In 2003 Nissan propose a new HEV
charge/discharge control system
based on car navigation
information. (Proceedings: JSAE
Annual Congress)
NISSAN MOTORS - Technology approach
Event
Output
Effect
Action
Various Methods of
Power Management
Generator control unit allows charging
to permit amount and controls
deceleration from becoming too large.
JP2001078306 (1997)
Regenerative braking
The battery management system
provides an actuator command for
control of electric power input upon
charging the battery pack in response
to the current value of BT
JP10295045 (1997)
Regenerative barking
JP2001268707 (1996)
Restarted after an
idiling stop released
JP10084636 (1995)
High speed
JP11136808 (1994)
High speed &
regenerative braking
Power generated/
consumed
Overcharge
Over discharge
Power management
Restricting the charge of DC-battery to
a proper amount by restricting the IC
engine output torque.
Controlling the max. power generation
output of generator and max. number
of rotations of engine depending on
the battery condition.
A control unit with a microcomputer
controls the generated power of the
engine-drive generator based on the
discriminated results of the state of
the DC-battery.
Findings
• JP10295045 (1997):- Battery management system, received 21 forward
citations from all big names in a span of 5 years and self- cited twice the
same technology indicating strong technology strength and building on
its own technology.
• Patent and non-patent information indicate that Nissan’s has focused
much on circuit arrangements for charging or depolarizing batteries or
for supplying loads from batteries (H02J 7/00)
• Jointly worked with Sony corp. (1998) developing high power density
Li-ion battery for parallel HEV
• Proposed a novel charge/discharge control system based on car
navigation information.